However, others who are just as committed to reducing youngsters' risk of tobacco-associated cancer, heart disease and lung disease, don't think there is enough evidence to demonstrate that controlling who gets into a movie theater can reduce the likelihood kids will become smokers.

First, they said, no one has definitively demonstrated that watching others smoke onscreen leads to more smoking among those in the audience. Furthermore, they said, most of the studies purporting to show that link are muddied by many other factors in kids' lives.

"Movies showing smoking might have a lot more in them that might appeal to youth at risk of smoking than just smoking," they wrote.

As a result, they discounted the strength of published estimates suggesting that 390,000 American youngsters smoke because of what they see onscreen, or that imposing adult ratings on films that include actors smoking would likely prevent 200,000 youngsters from becoming smokers. The figures fail to take into account that kids are drawn to smoking by far more than just what they see at the movies, they said.

Adult Film Ratings Don't Shield Kids From Other Images of Smoking

A third element of their opposition to tougher ratings is that singling out the movie industry ignores the many other media that contain images of smoking, including the Internet.

On a more practical level, the two called adult ratings a "highly inefficient way" of shielding youngsters from depictions of smoking. Kids can easily do an end run around restrictions by watching movies at friends' houses or downloading them either legally, or illegally, from the Web.

Finally, as a matter of principle, they objected to censorship of movies, books, art or theater as a means of tackling public health issues. Chapman and Farrelly suggested that censorship might turn off citizens and politicians who would otherwise support stricter tobacco control measures, such as blocking "commercial product placement by the tobacco industry."

They suggested that movies and other media can promote not just the interests of government or policymakers but also act as a mirror and "reflect on what is in society."